UV LED Tunnel Injection Layer for Hole Transport
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Solution Overview
Problem
Existing UV light emitting diodes (LEDs) face challenges in achieving high quantum efficiency and reducing parasitic luminescence at shorter wavelengths due to the difficulty in p-doping AlGaN layers with high aluminum content, leading to poor carrier injection and high electron leakage current.
Innovation Solution
Incorporating a thin doped or undoped AlN or AlGaN injection layer between the active zone and the p-side of the UV LED, which improves hole injection and blocks electron leakage, allowing for a significant increase in internal and external quantum efficiency while reducing parasitic luminescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If p-doped AlGaN electron blocking layer is used to improve hole injection, then hole injection is improved, but electron leakage current increases at short wavelengths
Solution Approach 1:
The patent divides the electron blocking function into two separate layers: a thin undoped AlN layer (1-5 nm) that blocks electrons, and a p-doped AlGaN layer that provides hole injection. This segmentation allows each layer to perform its specific function without the conflicting requirements that plague the conventional single-layer approach.
Solution Approach 2:
The undoped AlN layer acts as an intermediary between the active region and the p-doped AlGaN layer. It mediates the conflict between electron blocking and hole injection by providing a thin barrier that electrons cannot penetrate, while still allowing holes to be injected effectively by the adjacent p-doped layer.
2Use of energy by moving object
If high aluminum content AlGaN is used for deep UV wavelengths, then band-gap energy increases, but p-doping becomes difficult due to high ionization energy
Solution Approach 1:
The patent separates the functions of achieving deep UV band-gap energy and providing p-doping into different layers. The undoped AlN layer provides the high band-gap energy needed for deep UV emission, while the adjacent p-doped AlGaN layer provides the doping function, avoiding the need to p-dope high-aluminum-content AlGaN.
Solution Approach 2:
Instead of attempting to p-dope AlN or high-Al AlGaN (which is difficult or impossible), the patent uses a copy approach: it places a p-doped AlGaN layer adjacent to the undoped AlN layer, allowing the doping function to be performed by a material that is easier to dope, while the AlN layer maintains the required band-gap properties.
3Reliability
If thin injection layer is used to improve hole tunneling, then hole injection improves, but electron leakage blocking decreases
Solution Approach 1:
The patent segments the injection layer into two distinct layers with different thicknesses and doping states: a thin undoped AlN layer (1-5 nm) for electron blocking and a thicker p-doped AlGaN layer for hole injection. This segmentation resolves the contradiction by allowing each layer to be optimized for its specific function independently.
Solution Approach 2:
The patent applies local quality by making the AlN layer undoped and very thin specifically for electron blocking, while the adjacent AlGaN layer is p-doped and thicker for hole injection. Each region has locally optimized properties tailored to its specific function, rather than using a uniform structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a three-fold improvement in quantum efficiency and a substantial reduction in electron leakage current, enhancing the overall performance of UV LEDs, particularly in the deep UV region.
Implementation Method 1
the thickness of the injection layer is critical. It must be thin enough to allow hole tunneling to the active layer
Implementation Method 2
the injection layer inhibits electron leakage current from the active zone into the p-doped area of the LED
Data Source
AI summary
An ultraviolet (UV) light emitting structure, a UV light emitting device, and a method of making a UV light emitting structure or device, wherein the UV light emitting structure or device has an AlN or AlGaN injection layer with high aluminum content between the light emitting active region and the p-doped layers and wherein the injection layer has a thickness such that holes can tunnel from the p-side of the semiconductor-based ultraviolet light emitting diode structure through the injection layer in the active zone and also reducing leakage electrons out of the active zone.